Method for transmitting signal by wireless power transmitter in wireless charging system, wireless power transmitter and wireless power receiver

ABSTRACT

A method of transmitting a signal by a wireless power transmitter in a wireless charging system, wireless power transmitter, and a wireless power receiver are provided. The method includes transmitting a first signal; transmitting a second signal; detecting a load change during a period in which the second signal is transmitted; and extending a transmission period of the second signal based on the detected load change. The wireless power transmitter includes a power transmission unit configured to transmit a first signal and a second signal; a sensing unit configured to detect a load change during a period in which the second signal is transmitted; and a controller configured to extend a transmission period of the second signal based on the detected load change.

PRIORITY

This application claims priority under 35 U.S.C. §119(e) to a UnitedStates Provisional patent application filed in the United States Patentand Trademark Office on Jun. 24, 2014 and assigned Ser. No. 62/016,310,the entire content of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to wireless charging, and moreparticularly, to a method for transmitting signals by a wireless powertransmitter in a wireless charging system, the wireless powertransmitter, and a wireless power receiver.

2. Description of the Related Art

In view of their nature, mobile terminals such as portable phones andPersonal Digital Assistants (PDAs) are powered by rechargeablebatteries. To charge the batteries, the mobile terminals supplyelectrical energy to the batteries through separate chargers. Typically,the charger and the battery each have an exterior contact terminal andthus are electrically connected to each other by contacting theircontact terminals.

This contact-based charging scheme faces the problem of vulnerability ofcontact terminals to contamination of foreign materials and theresulting unreliable battery charging because the contact terminalsprotrude outward. Moreover, if the contact terminals are exposed tomoisture, the batteries may not be charged properly.

To address the above problem, wireless charging or contactless chargingtechnologies have recently been developed and applied to many electronicdevices.

Such a wireless charging technology is based on wireless powertransmission and reception. For example, once a portable phone is placedon a charging pad without being connected to an additional chargingconnector, its battery is automatically charged. Among wirelesslycharged products, wireless electric toothbrushes or wireless electricshavers are well known. The wireless charging technology offers thebenefits of increased waterproofness due to wireless charging ofelectronic products and enhanced portability due to no need for a wiredcharger for electronic devices. Further, it is expected that variousrelevant wireless charging technologies will be further developed in theupcoming era of electric vehicles.

There are mainly three wireless charging schemes: an electromagneticinduction scheme using coils, a resonance-based scheme, and a RadioFrequency (RF)/microwave radiation scheme based on the conversion ofelectrical energy to microwaves.

To date, the electromagnetic induction-based wireless charging scheme ismost popular. However, considering recent successful experiments inwireless power transmission over microwaves at a distance of tens ofmeters in Korea and in other overseas countries, it is foreseeable thatevery electronic product will be charged wirelessly at any time in anyplace in the near future.

Electromagnetic induction-based power transmission refers to powertransfer between primary and secondary coils. When a magnet moves arounda coil, a current is induced. Based on this principle, a transmittergenerates a magnetic field and a receiver produces energy by a currentinduced by a change in the magnetic field. This phenomenon is calledmagnetic induction and power transmission based on magnetic induction ishighly efficient in energy transfer.

Regarding resonance-based wireless charging, a system was suggested forwireless energy transfer from a charger at a distance of a few metersbased on the resonance-based power transmission principle by the coupledmode theory. Electromagnetic waves were resonated to carry electricalenergy, instead of sound. The resonant electrical energy is directlytransferred only in the presence of a device having the same resonantfrequency, while the unused electrical energy is reabsorbed into theelectromagnetic field rather being dispersed in the air. Thus, theresonant electrical energy does not affect nearby machines or humanbeings, as compared to other electrical waves.

A method in which a wireless power transmitter (or a Power TransmittingUnit (PTU)) detects or determines whether a wireless power receiver (orPower Receiving Unit (PRU)) is placed thereon may include a method ofdetecting a change in impedance of a power transmission unit included inthe wireless power transmitter.

If a wireless power transmitter (PTU) detects the presence of a wirelesspower receiver (PRU) through an impedance change detection and the like,the wireless power transmitter may initiate communication with thewireless power receiver by supplying the power with which the wirelesspower receiver can perform communication.

For example, in accordance with the wireless power standard of Alliancefor Wireless Power (A4WP), a wireless power transmitter may transmit along-beacon signal, and upon receiving the long-beacon signal, awireless power receiver may transmit an advertisement signal to thewireless power transmitter within a predetermined time, therebyproceeding with a registration procedure for wireless charging.

However, where a boot procedure for operating a processor is requiredwhile the battery power of the wireless power receiver is low ordepleted or the wireless power receiver is powered off, the wirelesspower receiver may not transmit the advertisement signal to the wirelesspower transmitter within a predetermined time. If the wireless powerreceiver cannot transmit the advertisement signal within a predeterminedtime in this way, the normal registration procedure may not beperformed, so wireless charging for the wireless power receiver may notbe possible.

SUMMARY

The present invention has been made to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below.

Accordingly, an aspect of the present invention is to provide a signaltransmission method in which if a wireless power transmitter detects aload change before its transmission of a long-beacon signal isterminated, the wireless power transmitter may extend a transmissionperiod of the long-beacon signal to receive an advertisement signal in awireless charging system, and to provide a wireless power transmitterand a wireless power receiver.

Another aspect of the present invention is to provide a signaltransmission method in which if a wireless power transmitter receives abeacon extension request signal before its transmission of a long-beaconsignal is terminated, the wireless power transmitter may extend atransmission period of the long-beacon signal to receive anadvertisement signal in a wireless charging system, and to provide awireless power transmitter and a wireless power receiver.

In accordance with an aspect of the present invention, there is provideda method of transmitting a signal by a wireless power transmitter in awireless charging system. The method includes transmitting a firstsignal; transmitting a second signal; detecting a load change during aperiod in which the second signal is transmitted; and extending atransmission period of the second signal based on the detected loadchange.

In accordance with another aspect of the present invention, there isprovided a wireless power transmitter. The wireless power transmitterincludes a power transmission unit configured to transmit a first signaland a second signal; a sensing unit configured to detect a load changeduring a period in which the second signal is transmitted; and acontroller configured to extend a transmission period of the secondsignal based on the detected load change.

In accordance with another aspect of the present invention, there isprovided a wireless power receiver. The wireless power receiver includesa power reception unit configured to receive a first signal and a secondsignal; a control circuit that is electrically connected to the powerreception unit, and configured to generate a control signal for a loadchange based on the first signal or the second signal received from thepower reception unit; and a switching unit that is provided between thepower reception unit and a load, and configured to switch a connectionbetween the power reception unit and the load based on the controlsignal from the control circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram of an overall operation of a wireless chargingsystem;

FIG. 2 is a block diagram of a wireless power transmitter and a wirelesspower receiver according to an embodiment of the present invention;

FIG. 3 is a block diagram of a wireless power transmitter and a wirelesspower receiver according to an embodiment of the present invention;

FIG. 4 is a flow diagram of a signal flow for operations of a wirelesspower transmitter and a wireless power receiver according to anembodiment of the present invention;

FIG. 5 is a flowchart of a method of a wireless power transmitter and awireless power receiver according to an embodiment of the presentinvention;

FIG. 6 is a graph illustrating amounts of power applied by a wirelesspower transmitter with respect to a time axis according to an embodimentof the present invention;

FIG. 7 is a flowchart of a method of controlling a wireless powertransmitter according to an embodiment of the present invention;

FIG. 8 is a graph illustrating amounts of power applied by a wirelesspower transmitter with respect to a time axis according to the flowchartof FIG. 7;

FIG. 9 is a flowchart of a method of controlling a wireless powertransmitter according to an embodiment of the present invention;

FIG. 10 is a graph illustrating amounts of power supplied by a wirelesspower transmitter with respect to a time axis according to the flowchartof FIG. 9;

FIG. 11 is a block diagram of a wireless power transmitter and awireless power receiver in a Stand Alone (SA) mode according to anembodiment of the present invention;

FIG. 12 is a graph illustrating transmission of a beacon signalaccording to an embodiment of the present invention;

FIG. 13 is a graph illustrating transmission of a beacon signalaccording to an embodiment of the present invention;

FIG. 14 is a flowchart illustrating a beacon signal transmissionprocedure according to an embodiment of the present invention;

FIG. 15 is a graph illustrating transmission of a beacon signalaccording to an embodiment of the present invention;

FIG. 16 is a flowchart illustrating a beacon signal transmissionprocedure according to an embodiment of the present invention; and

FIG. 17 is a block diagram of a wireless power receiver according to anembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of the presentinvention as defined by the appended claims and their equivalents.Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures. It includes variousdetails to assist in that understanding but these are to be regarded asmerely exemplary. Accordingly, those of ordinary skilled in the art willrecognize that various changes and modifications of the embodiments ofthe present invention described herein can be made without departingfrom the scope and spirit of the present invention. In addition,descriptions of well-known functions and constructions may be omittedfor clarity and conciseness.

The terms and words used in the following description and claims are notlimited to their dictionary meanings, but, are merely used to enable aclear and consistent understanding of the present invention.Accordingly, it should be apparent to those skilled in the art that thefollowing description of embodiments of the present invention isprovided for illustration purpose only and not for the purpose oflimiting the present invention as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

The term “substantially” indicates that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

A description will first be given of the concept of a wireless chargingsystem applicable to embodiments of the present invention with referenceto FIGS. 1 to 11, followed by a detailed description of a method fortransmitting a signal by a wireless power transmitter in a wirelesscharging system and of a wireless power transmitter and a wireless powerreceiver according to various embodiments of the present invention withreference to FIGS. 12 to 17.

FIG. 1 is a block diagram of an overall operation of a wireless chargingsystem.

Referring to FIG. 1, the wireless charging system includes a wirelesspower transmitter (or Power Transmitting Unit (PTU)) 100 and one or morewireless power receivers (or Power Receiving Units (PRUs)) 110-1, 110-2,. . . , and 110-n.

The wireless power transmitter 100 may wirelessly transmit power 1-1,1-2, . . . , and 1-n respectively to the wireless power receivers 110-1,110-2, . . . , and 110-n. In addition, the wireless power transmitter100 may wirelessly transmit the power 1-1, 1-2, . . . , and 1-n only towireless power receivers that have been authenticated in a predeterminedauthentication procedure.

The wireless power transmitter 100 may establish electrical connectionsto the wireless power receivers 110-1, 110-2, . . . , and 110-n. Forexample, the wireless power transmitter 100 may transmit wireless powerin the form of electromagnetic waves to the wireless power receivers110-1, 110-2, . . . , and 110-n.

The wireless power transmitter 100 may conduct bi-directionalcommunication with the wireless power receivers 110-1, 110-2, . . . ,and 110-n. The wireless power transmitter 100 and the wireless powerreceivers 110-1, 110-2, . . . , and 110-n may process ortransmit/receive packets 2-1, 2-2, . . . , and 2-n configured inpredetermined frames. The frames are described below in greater detail.A wireless power receiver may be configured as a mobile communicationterminal, a Personal Digital Assistant (PDA), a Personal MultimediaPlayer (PMP), a smartphone, or the like.

The wireless power transmitter 100 may apply power wirelessly to theplurality of wireless power receivers 110-1, 110-2, . . . , and 110-n.For example, the wireless power transmitter 100 may transmit power tothe plurality of wireless power receivers 110-1, 110-2, . . . , and110-n by resonance. If the wireless power transmitter 100 employs theresonance scheme, the distance between the wireless power transmitter100 and the wireless power receivers 110-1, 110-2, . . . , and 110-n maybe preferably 30 m or less. If the wireless power transmitter 100employs an electromagnetic induction scheme, the distance between thewireless power transmitter 100 and the wireless power receivers 110-1,110-2, . . . , and 110-n may be preferably 10 cm or less.

The wireless power receivers 110-1, 110-2, . . . , and 110-n may receivewireless power from the wireless power transmitter 100 and charge theirinternal batteries. Further, the wireless power receivers 110-1, 110-2,. . . , and 110-n may each transmit to the wireless power transmitter100 a signal requesting wireless power transmission, informationrequired for wireless power reception, wireless power receiver stateinformation, or control information for the wireless power transmitter100. Information on the transmitted signal is described below in greaterdetail.

Each of the wireless power receivers 110-1, 110-2, . . . , and 110-n mayalso transmit a message indicating its charged state to the wirelesspower transmitter 100.

The wireless power transmitter 100 may include a display means such as adisplay and may display the state of each wireless power receiver 110-1,110-2, . . . , and 110-n based on the messages received from thewireless power receivers 110-1, 110-2, . . . , and 110-n. Further, thewireless power transmitter 100 may display the time that is expecteduntil each of the wireless power receivers 110-1, 110-2, . . . , and110-n is completely charged.

The wireless power transmitter 100 may transmit a control signal fordisabling a wireless charging function to the wireless power receivers110-1, 110-2, . . . , and 110-n. Upon receipt of the control signal fordisabling the wireless charging function from the wireless powertransmitter 100, a wireless power receiver may disable the wirelesscharging function.

FIG. 2 is a block diagram of a wireless power transmitter and a wirelesspower receiver according to an embodiment of the present invention.

Referring to FIG. 2, a wireless power transmitter 200 may include atleast one of a power transmission unit 211, a controller 212, acommunication unit 213, a display unit 214, and a storage unit 215.

The power transmission unit 211 may supply power required by thewireless power transmitter 200 and may wirelessly supply power to awireless power receiver 250. The power transmission unit 211 may supplypower in the form of Alternating Current (AC) waveforms or by convertingpower in Direct Current (DC) waveforms to power in AC waveforms by meansof a converter. The power transmission unit 211 may be implemented as abuilt-in battery. Alternatively, the power transmission unit 211 may beimplemented as a power reception interface so as to receive powerexternally and supply the power to other components. It will beunderstood by those skilled in the art that as far as it can supplypower in AC waveforms, any means may be used as the power transmissionunit 211.

The controller 212 may provide overall control to the wireless powertransmitter 200. The controller 212 may control an overall operation ofthe wireless power transmitter 200 using an algorithm, a program, or anapplication required for a control operation, read from the storage unit215. The controller 212 may be implemented as a Central Processing Unit(CPU), a microprocessor, or a mini computer.

The communication unit 213 may communicate with the wireless powerreceiver 250 in a predetermined communication scheme. The communicationunit 213 may receive power information from the wireless power receiver250. The power information may include information about at least one ofthe capacity, residual battery amount, the number of charging, useamount, battery capacity, and battery proportion of the wireless powerreceiver 250.

Further, the communication unit 213 may transmit a charging functioncontrol signal for controlling the charging function of the wirelesspower receiver 250. The charging function control signal may be acontrol signal that enables or disables the charging function bycontrolling a power reception unit 251 of the specific wireless powerreceiver 250. In addition, the power information may include informationabout insertion of a wired charging terminal, transition from a StandAlone (SA) mode to a Non-Stand Alone (NSA) mode, error state release,and the like, as described below in detail.

In addition, the charging function control signal may includeinformation related to power control or a power control command to copewith an occurrence of an abnormality according to an embodiment of thepresent invention.

The communication unit 213 may receive a signal from another wirelesspower transmitter as well as the wireless power receiver 250. Forexample, the communication unit 213 may proceed with a registrationprocedure for wireless charging by receiving an advertisement signaltransmitted from a communication unit 253 of the wireless power receiver250.

The controller 212 may display a state of the wireless power receiver250 on the display unit 214 based on a message received from thewireless power receiver 250 through the communication unit 213. Further,the controller 212 may display on the display unit 214 the time that isexpected until the wireless power receiver 250 is completely charged.

As illustrated in FIG. 2, the wireless power receiver 250 may include atleast one of a power reception unit 251, a controller 252, acommunication unit 253, a display unit 258, and a storage unit 259.

The power reception unit 251 may receive power wirelessly from thewireless power transmitter 200. The power reception unit 251 may receivepower in the form of AC waveforms from the wireless power transmitter200.

The controller 252 may provide overall control to the wireless powerreceiver 250. The controller 252 may control an overall operation of thewireless power receiver 250 using an algorithm, a program, or anapplication required for a control operation, read from the storage unit259. The controller 252 may be implemented as a CPU, a microprocessor,or a mini computer.

The communication unit 253 may communicate with the wireless powertransmitter 200 in a predetermined communication scheme. Thecommunication unit 253 may transmit power information to the wirelesspower transmitter 200. The power information may include informationabout at least one of the capacity, residual battery amount, the numberof charging, use amount, battery capacity, and battery proportion of thewireless power receiver 250.

Further, the communication unit 253 may transmit a charging functioncontrol signal for controlling the charging function of the wirelesspower receiver 250. The charging function control signal may be acontrol signal that enables or disables the charging function bycontrolling the power reception unit 251 of the wireless power receiver250. Alternatively, the power information may include information aboutinsertion of a wired charging terminal, transition from the SA mode tothe NSA mode, error state release, and the like, as described below indetail. Further, the charging function control signal may includeinformation related to power control or a power control command to copewith an occurrence of an abnormality according to an embodiment of thepresent invention.

Moreover, the communication unit 253 may receive a beacon signaltransmitted from the power transmission unit 211 of the wireless powertransmitter 200 through the power reception unit 251, and transmit anadvertisement signal to the wireless power transmitter 200 within apredetermined time, thereby proceeding with a registration procedure forwireless charging.

The controller 252 may display a state of the wireless power receiver250 on the display unit 258. Further, the controller 252 may display onthe display unit 258 the time that is expected until the wireless powerreceiver 250 is completely charged.

FIG. 3 is a detailed block diagram of a wireless power transmitter and awireless power receiver according to an embodiment of the presentinvention.

Referring to FIG. 3, the wireless power transmitter 200 may include atleast one of a Transmission (Tx) resonator 211 a, the controller 212(for example, a Micro Controller Unit (MCU)), the communication unit 213(for example, an out-of-band signaling unit), a matching unit 216, adriver (e.g. power supply) 217, a Power Amplifier (PA) 218, and asensing unit 219. The wireless power receiver 250 may include at leastone of a Reception (Rx) resonator 251 a, the controller 252, a controlcircuit 252 a, the communication unit 253, a rectifier 254, a DC/DCconverter 255, a switching unit 256, and a loading unit (or a clientdevice load) 257.

The driver 217 may output DC power having a predetermined voltage value.The voltage value of the DC power output from the driver 217 may becontrolled by the controller 212.

A DC current output from the driver 217 may be applied to the PA 218.The PA 218 may amplify the DC current with a predetermined gain.Further, the PA 218 may convert DC power to AC power based on a signalreceived from the controller 212. Therefore, the PA 218 may output ACpower.

The matching unit 216 may perform impedance matching. For example, thematching unit 216 may control the impedance viewed from the matchingunit 216 so that its output power may have high efficiency or highpower. The sensing unit 219 may sense a load change by the wirelesspower receiver 250 through the Tx resonator 211 a or the PA 218 and mayprovide the sensing result to the controller 212.

According to an embodiment of the present invention, when the wirelesspower transmitter 200 transmits a short-beacon signal or a long-beaconsignal to the wireless power receiver 250, the wireless power receiver250 may generate a load change by means of a predetermined circuit andthe like. The sensing unit 219 of the wireless power transmitter 200 maydetect a load change of the wireless power receiver 250, and provide theload change detection results to the controller 212. According to anembodiment of the present invention, the controller 212 may detect thepresence of the wireless power receiver 250 or may extend or adjust atransmission period of the beacon signal (e.g., the long-beacon signal),based on the load change detected by the sensing unit 219.

The matching unit 216 may adjust impedance under control of thecontroller 212. The matching unit 216 may include at least one of a coiland a capacitor. The controller 212 may control a connection to at leastone of the coil and the capacitor and thus may perform impedancematching accordingly.

The Tx resonator 211 a may transmit input AC power to the Rx resonator251 a. The Tx resonator 211 a and the Rx resonator 251 a may beimplemented as resonant circuits having the same resonant frequency. Forexample, the resonant frequency may be determined to be 6.78 MHz.

The communication unit 213 may communicate with the communication unit253 of the wireless power receiver 250, for example, bi-directionally ata frequency of 2.4 GHz (by Wireless Fidelity (WiFi), ZigBee, orBluetooth (BT)/Bluetooth Low Energy (BLE)).

The Rx resonator 251 a may receive power for charging. Further, the Rxresonator 251 a may receive a beacon signal (e.g., a short-beacon signalor a long-beacon signal) transmitted through the Tx resonator 211 a ofthe wireless power transmitter 200.

The rectifier 254 may rectify wireless power received from the Rxresonator 251 a to DC power. For example, the rectifier 254 may beimplemented in the form of a diode bridge. The DC/DC converter 255 mayconvert the rectified power with a predetermined gain. For example, theDC/DC converter 255 may convert the rectified power so that the voltageof its output may be 5V. A minimum voltage value and a maximum voltagevalue that may be applied to the input of the DC/DC converter 255 may bepreset.

The switching unit 256 may connect the DC/DC converter 255 to theloading unit 257. The switching unit 256 may be kept in an ON or OFFstate under the control of the controller 252. The switching unit 256 isoptional. If the switching unit 256 is in the ON state, the loading unit257 may store the converted power received from the DC/DC converter 255.

According to an embodiment of the present invention, the control circuit252 a may generate a control signal for controlling the switching unit256 based on the signal received through the Rx resonator 251 a of thewireless power receiver 250. For example, the control circuit 252 a,unlike the controller 252, is driven by the signal (e.g., a short-beaconsignal or a long-beacon signal) received at the wireless power receiver250, so the control circuit 252 a may generate a load change bycontrolling the switching unit 256. According to an embodiment of thepresent invention, as the control circuit 252 a is provided as describedabove, a load change of the wireless power receiver 250 may be generatedeven though no power is supplied to the controller 252 or the controller252 is disabled.

Further, according to an embodiment of the present invention, thecontrol circuit 252 a may generate a code or a signal of a predeterminedpattern based on the signal received (e.g., a short-beacon signal or along-beacon signal) received through the Rx resonator 251 a of thewireless power receiver 250. The load switch (e.g., the switching unit256) may be controlled by the code or signal generated in the controlcircuit 252 a, making it possible to generate a load changecorresponding to a predetermined code or signal. The wireless powertransmitter 200 may detect a load change of the wireless power receiver250 and decode a predetermined code or signal, thereby obtainingpredetermined information (e.g., information relating to the extensionof a beacon signal period).

FIG. 4 is a flow diagram of a signal flow for operations of a wirelesspower transmitter and a wireless power receiver according to anembodiment of the present invention.

Referring to FIG. 4, a wireless power transmitter 400 may be powered onin step S401. Upon power-on, the wireless power transmitter 400 mayconfigure an environment in step S402.

The wireless power transmitter 400 may enter a power save mode in stepS403. In the power save mode, the wireless power transmitter 400 mayapply different types of power beacons for detection, with theirrespective periods, which are described below in greater detail withreference to FIG. 6. For example, the wireless power transmitter 400 maytransmit power beacons 5404 and 5405 for detection (for example, shortbeacons or long beacons) and the power beacons 5404 and 5405 may havedifferent power values. One or both of the power beacons 5404 and 5405for detection may have sufficient power to drive the communication unitof a wireless power receiver 450. For example, the wireless powerreceiver 450 may communicate with the wireless power transmitter 400 bydriving its communication unit by means of one or both of the powerbeacons 5404 and 5405 for detection. This state may be referred to as anull state.

The wireless power transmitter 400 may detect a load change as thewireless power receiver 450 is placed on the wireless power transmitter400. The wireless power transmitter 400 may enter a low power mode instep S408. The low power mode is described below in greater detail withreference to FIG. 6. The wireless power receiver 450 may drive itscommunication unit based on the power received from the wireless powertransmitter 400 in step S409.

The wireless power receiver 450 may transmit a PTU searching signal tothe wireless power transmitter 400 in step S410. The wireless powerreceiver 450 may transmit the PTU searching signal as a BLE-basedAdvertisement (AD) signal. The wireless power receiver 450 may transmitthe PTU searching signal periodically until it receives a responsesignal from the wireless power transmitter 400 or a predetermined timeperiod lapses.

Upon receipt of the PTU searching signal from the wireless powerreceiver 450, the wireless power transmitter 400 may transmit a PRUresponse signal in step S411. The PRU response signal may establish aconnection between the wireless power transmitter 400 and the wirelesspower receiver 450.

The wireless power receiver 450 may transmit a PRU static signal in stepS412. The PRU static signal may indicate a state of the wireless powerreceiver 450 and may request joining in a wireless power network managedby the wireless power transmitter 400.

The wireless power transmitter 400 may transmit a PTU static signal instep S413. The PTU static signal transmitted by the wireless powertransmitter 400 may indicate capabilities of the wireless powertransmitter 400.

After the wireless power transmitter 400 and the wireless power receiver450 transmit and receive the PRU static signal and the PTU staticsignal, the wireless power receiver 450 may transmit a PRU dynamicsignal periodically in steps S414 and S415. The PRU dynamic signal mayinclude at least one parameter measured by the wireless power receiver450. For example, the PRU dynamic signal may include information about avoltage at the output of a rectifier of the wireless power receiver 450.The state of the wireless power receiver 450 may be referred to as aboot state in step S407.

The wireless power transmitter 400 enters a power transfer mode in stepS416. The wireless power transmitter 400 may transmit a PRU controlsignal or a command signal for enabling charging to the wireless powerreceiver 450 in step S417. In the power transfer mode, the wirelesspower transmitter 400 may transmit charging power.

The PRU control signal transmitted by the wireless power transmitter 400may include information that enables/disables charging of the wirelesspower receiver 450 and permission information. The PRU control signalmay be transmitted each time a charged state is changed. For example,the PRU control signal may be transmitted every 250 ms or upon anoccurrence of a parameter change. The PRU control signal may beconfigured to be transmitted within a predetermined threshold time, forexample, within 1 second, even though no parameter is changed.

The wireless power receiver 450 may change settings according to the PRUcontrol signal and transmit a PRU dynamic signal to report a state ofthe wireless power receiver 450 in steps S418 and S419. The PRU dynamicsignal transmitted by the wireless power receiver 450 may includeinformation about at least one of a voltage, a current, a wireless powerreceiver state, and a temperature. The state of the wireless powerreceiver 450 may be referred to as an ON state.

The PRU dynamic signal may have the following data structure illustratedin Table 1 below.

TABLE 1 Field Octets Description Use Units Optional 1 Defines whichoptional Mandatory fields fields are populated V_(RECT) 2 Voltage atdiode output Mandatory mV I_(RECT) 2 Current at diode output MandatorymA V_(OUT) 2 Voltage at charge/ Optional mV battery port I_(OUT) 2Current at charge/ Optional mA battery port Temperature 1 Temperature ofPRU Optional Deg C. from −40 C. V_(RECT)_MIN_DYN 2 V_(RECT)_LOW_LIMITOptional mV (dynamic value) V_(RECT)_SET_DYN 2 Desired V_(RECT) OptionalmV (dynamic value) V_(RECT)_HIGH_DYN 2 V_(RECT)_HIGH_LIMIT Optional mV(dynamic value) PRU alert 1 Warnings Mandatory Bit field RFU 3 Undefined

Referring to Table 1 above, the PRU dynamic signal may include one ormore fields. The fields may provide optional field information,information about a voltage at the output of the rectifier of thewireless power receiver 450, information about a current at the outputof the rectifier of the wireless power receiver 450, information about avoltage at the output of the DC/DC converter of the wireless powerreceiver 450, information about a current at the output of the DC/DCconverter of the wireless power receiver 450, temperature information,information about a minimum voltage value V_(RECT) _(—) _(MIN) _(—)_(DYN) at the output of the rectifier of the wireless power receiver450, information about an optimum voltage value V_(RECT) _(—) _(SET)_(—) _(DYN) at the output of the rectifier of the wireless powerreceiver 450, information about a maximum voltage value V_(RECT) _(—)_(HIGH) _(—) _(DYN) at the output of the rectifier of the wireless powerreceiver 450, and warning information (e.g. PRU alert). The PRU dynamicsignal may include at least one of the above fields.

For example, at least one voltage set value that has been determinedaccording to a charging situation (for example, the information about aminimum voltage value V_(RECT) _(—) _(MIN) _(—) _(DYN) at the output ofthe rectifier of the wireless power receiver 450, the information aboutan optimum voltage value V_(RECT) _(—) _(SET) _(—) _(DYN) at the outputof the rectifier of the wireless power receiver 450, and the informationabout a maximum voltage value V_(RECT) _(—) _(HIGH) _(—) _(DYN) at theoutput of the rectifier of the wireless power receiver 450) may betransmitted in the at least one field of the PRU dynamic signal. Uponreceipt of the PRU dynamic signal, the wireless power transmitter 400may adjust a wireless charging voltage to be transmitted to eachwireless power receiver 450 based on the voltage value set in the PRUdynamic signal.

Among the fields, PRU alert may be configured in the data structureillustrated in Table 2 below.

TABLE 2 7 6 5 4 3 2 1 0 Overvoltage Overcurrent Overtemp Charge TATransition restart RFU complete detect request

Referring to Table 2 above, PRU alert may include a bit for restartrequest, a bit for transition, and a bit for Travel Adapter (TA) detect.The TA detect bit indicates that a wireless power receiver 450 has beenconnected to a wired charging terminal in the wireless power transmitter400 that provides wireless charging. The transition bit informs thewireless power transmitter 400 that the wireless power receiver 450 isreset before a communication Integrated Circuit (IC) of the wirelesspower receiver 450 transitions from the SA mode to the NSA mode.Finally, the restart request bit indicates that the wireless powertransmitter 400 is ready to resume charging of the wireless powerreceiver 450, when the wireless power transmitter 400 that hasdiscontinued charging by reducing transmission power due to overcurrentor overtemperature returns to a normal state.

PRU alert may also be configured in the data structure illustrated inTable 3 below.

TABLE 3 7 6 5 4 3 2 1 0 PRU PRU PRU PRU Self Charge Wired Mode Modeover-voltage over-current over-temperature Protection Complete ChargerTransition Transition Detect Bit 1 Bit 0

Referring to Table 3 above, PRU alert may include the fields ofovervoltage, overcurrent, overtemperature, PRU Self Protection, ChargeComplete, Wired Charger Detect, and Mode Transition. If the overvoltagefield is set to “1,” this may imply that the voltage Vrect of thewireless power receiver 450 has exceeded an overvoltage limit. Theovercurrent and overtemperature fields may be set in the same manner asthe overvoltage field. PRU Self Protection indicates that the wirelesspower receiver 450 protects itself by directly reducing power across aload. In this case, the wireless power transmitter 400 does not need tochange a charged state.

According to an embodiment of the present invention, bits for ModeTransition may be set to a value for notifying the wireless powertransmitter 400 of the duration of a mode transition. The ModeTransition bits may be configured as illustrated in Table 4 below.

TABLE 4 Value(Bit) Mode Transition Bit Description 00 No Mode Transition01 2 s Mode Transition time limit 10 3 s Mode Transition time limit 11 6s Mode Transition time limit

Referring to Table 4 above, if the Mode Transition bits are set to “00,”this may indicate no mode transition. If the Mode Transition bits areset to “01,” this may indicate that a time limit for completion of amode transition is 2 seconds. If the Mode Transition bits are set to“10,” this may indicate that the time limit for completion of a modetransition is 3 seconds. If the Mode Transition bits are set to “11,”this may indicate that the time limit for completion of a modetransition is 6 seconds.

For example, if a mode transition takes 3 seconds or less, the ModeTransition bits may be set to “10.” Before starting a mode transition,the wireless power receiver 450 may ensure that no impedance change willoccur during the mode transition by changing an input impedance settingto match a 1.1 W power draw. Accordingly, the wireless power transmitter400 adjusts power ITX_COIL for the wireless power receiver 450 accordingto this setting and thus may maintain the power ITX_COIL for thewireless power receiver 450 during the mode transition.

Therefore, after a mode transition duration is set by the ModeTransition bits, the wireless power transmitter 400 may maintain thepower ITX_COIL for the wireless power receiver 450 during the modetransition duration, for example, for 3 seconds. In other words, eventhough the wireless power transmitter 400 does not receive a responsefrom the wireless power receiver 450 for 3 seconds, the wireless powertransmitter 400 may maintain a connection to the wireless power receiver450. However, after the mode transition duration lapses, the wirelesspower transmitter 400 may end the power transmission, considering thatthe wireless power receiver 450 is a rogue object.

The wireless power receiver 450 may sense an occurrence of an error. Thewireless power receiver 450 may transmit a warning signal to thewireless power transmitter 400 in step S420. The warning signal may betransmitted as a PRU dynamic signal or an alert signal. For example, thewireless power receiver 450 may transmit the PRU alert field illustratedin Table 1 above to indicate an error state to the wireless powertransmitter 400. Alternatively, the wireless power receiver 450 maytransmit a stand-alone warning signal indicating an error state to thewireless power transmitter 400. Upon receipt of the warning signal, thewireless power transmitter 400 may enter a latch fault mode in stepS422. The wireless power receiver 450 may enter a null state in stepS423.

FIG. 5 is a flowchart of a method of a wireless power transmitter and awireless power receiver according to another embodiment of the presentinvention. The control method in FIG. 5 is described in detail withreference to FIG. 6. FIG. 6 is a graph illustrating amounts of powerapplied by a wireless power transmitter 400 with respect to a time axisin accordance with FIG. 5.

Referring to FIG. 5, the wireless power transmitter 400 may start tooperate in step S501. Further, the wireless power transmitter 400 mayreset an initial setting in step S503 and may enter the power save modein step S505. The wireless power transmitter 400 may apply differenttypes of power having different power amounts to the power transmissionunit in the power save mode. For example, the wireless power transmittermay apply second detection power 601 and 602 and third detection power611 to 615 to the power transmission unit in FIG. 6. The wireless powertransmitter 400 may apply the second detection power 601 and 602periodically with a second period. When the wireless power transmitter400 supplies the second detection power 601 and 602, the seconddetection power 601 and 602 may last for a second time duration. Thewireless power transmitter 400 may apply the third detection power 611to 615 periodically with a third period. When the wireless powertransmitter 400 supplies the third detection power 611 to 615, the thirddetection power 611 to 615 may last for a third time duration. The thirddetection power 611 to 615 may have the same power value, or differentpower values as illustrated in FIG. 6.

After outputting the third detection power 611, the wireless powertransmitter 400 may output the third detection power 612 having the samepower amount. If the wireless power transmitter 400 outputs thirddetection power 612 having the same amount as described above, the thirddetection power 612 may have a power amount sufficient to detect thesmallest wireless power receiver 450, for example, a wireless powerreceiver of category 1.

On the other hand, after outputting the third detection power 611, thewireless power transmitter 400 may output the third detection power 612having a different power amount. If the wireless power transmitter 400outputs different amounts of third detection power as described above,the respective power amounts of the third detection power may besufficient to detect wireless power receivers of category 1 to category5. For example, the third detection power 611 may have a power amountsufficient to detect a wireless power receiver 450 of category 5, thethird detection power 612 may have a power amount sufficient to detect awireless power receiver of category 3, and the third detection power 613may have a power amount sufficient to detect a wireless power receiver450 of category 1.

The second detection power 601 and 602 may drive the wireless powerreceiver 450. In addition, the second detection power 601 and 602 mayhave a power amount sufficient to drive the controller and/or thecommunication unit of the wireless power receiver 450.

The wireless power transmitter 400 may apply the second detection power601 and 602 and the third detection power 611 to 615 respectively withthe second and third periods to the power transmission unit. If thewireless power receiver 450 is placed on the wireless power transmitter400, an impedance viewed from a point of view of the wireless powertransmitter 400 may be changed. The wireless power transmitter 400 maydetect an impedance change during an application of the second detectionpower 601 and 602 and the third detection power 611 to 615. For example,the wireless power transmitter 400 may detect an impedance change duringan application of the third detection power 615. Therefore, the wirelesspower transmitter 400 may detect an object in step S507 in FIG. 5. If noobject is detected in step S507, the wireless power transmitter 400 maybe kept in the power save mode in which it applies different types ofpower periodically in step S505.

If the wireless power transmitter 400 detects an object due to animpedance change in step S507, the wireless power transmitter may enterthe low power mode in step 509. In the low power mode, the wirelesspower transmitter 400 applies a driving power having a power amountsufficient to drive the controller and the communication unit of thewireless power receiver 450. For example, the wireless power transmitter400 may apply driving power 620 to the power transmission unit in FIG.6. The wireless power receiver 450 may receive the driving power 620 anddrive the controller and/or the communication unit with the drivingpower 620. The wireless power receiver 450 may communicate with thewireless power transmitter 400 with the driving power 620 in apredetermined communication scheme. For example, the wireless powerreceiver 450 may transmit and receive data required for authenticationand may join a wireless power network managed by the wireless powertransmitter 400 based on the data. However, if a rogue object is placedinstead of a wireless power receiver 450, data transmission andreception may not be performed. Therefore, the wireless powertransmitter 400 may determine whether the object is a rogue object instep S511 in FIG. 5. For example, if the wireless power transmitter 400fails to receive a response from the object for a predetermined time,the wireless power transmitter 400 may determine the object as a rogueobject.

If the wireless power transmitter 400 determines the object as a rogueobject in step S511, the wireless power transmitter 400 may enter thelatch fault mode in step S513. On the contrary, if the wireless powertransmitter 400 determines that the object is not a rogue object in stepS511, the wireless power transmitter 400 may proceed with a joiningoperation in step S519. For example, the wireless power transmitter 400may apply first power 631 to 634 periodically with a first period inFIG. 6. The wireless power transmitter 400 may detect an impedancechange during an application of the first power. For example, if therogue object is removed in step S515 in FIG. 5, the wireless powertransmitter 400 may detect an impedance change and thus determine thatthe rogue object has been removed. On the contrary, if the rogue objectis not removed in step S515, the wireless power transmitter 400 may notdetect an impedance change and thus may determine that the rogue objecthas not been removed. If the rogue object has not been removed, thewireless power transmitter 400 may notify a user that the wireless powertransmitter 400 is currently in an error state by performing at leastone of illuminating a lamp or outputting a warning sound. Accordingly,the wireless power transmitter 400 may include an output unit forilluminating a lamp and/or outputting a warning sound.

If it is determined that the rogue object has not been removed in stepS515, the wireless power transmitter 400 may maintain the latch faultmode in step S513. On the other hand, if the rogue object has beenremoved in step S515, the wireless power transmitter may reenter thepower save mode in step S517. For example, the wireless powertransmitter may apply second power 651 and 652 and third power 661 to665 in FIG. 6.

As described above, if a rogue object is placed on the wireless powertransmitter 400, instead of a wireless power receiver 450, the wirelesspower transmitter 400 may enter the latch fault mode. Further, thewireless power transmitter 400 may determine whether the rogue objecthas been removed, based on an impedance change that occurs according topower applied in the latch fault mode. That is, a condition of entry tothe latch fault mode may be the presence of a rogue object in theembodiment illustrated in FIGS. 5 and 6. In addition to the presence ofa rogue object, the wireless power transmitter 400 may have many otherconditions for entry to the latch fault mode. For example, the wirelesspower transmitter 400 may be cross-connected to a wireless powerreceiver 450 placed on another wireless power transmitter. In this case,the wireless power transmitter 400 may also enter the latch fault mode.

When the wireless power transmitter 400 is cross-connected to a wirelesspower receiver 450, the wireless power transmitter 400 must return to aninitial state and the wireless power receiver 450 should be removed. Thewireless power transmitter 400 may set a cross connection of a wirelesspower receiver 450 placed on another wireless power transmitter, thatis, joining of a wireless power receiver 450 placed on another wirelesspower transmitter in a wireless power network managed by the wirelesspower transmitter 450 as a condition for entry to the latch fault mode.An operation of a wireless power transmitter 400 upon an occurrence ofan error such as a cross connection is described below with reference toFIG. 7.

FIG. 7 is a flowchart of a method of controlling a wireless powertransmitter according to an embodiment of the present invention. Thecontrol method of FIG. 7 will be described in detail with reference toFIG. 8. FIG. 8 is a graph illustrating amounts of power supplied by awireless power transmitter 400 with respect to a time axis according tothe flowchart of FIG. 7.

Referring to FIG. 7, the wireless power transmitter 400 may start tooperate in step S701. Further, the wireless power transmitter 400 mayreset an initial setting in step S703 and may enter the power save modein step S705. The wireless power transmitter 400 may apply differenttypes of power having different power amounts to the power transmissionunit in the power save mode. For example, the wireless power transmittermay apply second detection power 801 and 802 and third detection power811 to 815 to the power transmission unit in FIG. 8. The wireless powertransmitter 400 may apply the second detection power 801 and 802periodically with a second period. When the wireless power transmitter400 applies the second detection power 801 and 802, the second detectionpower 801 and 802 may last for a second time duration. The wirelesspower transmitter may apply the third detection power 811 to 815periodically with a third period. When the wireless power transmitterapplies the third detection power 811 to 815, the third detection power811 to 815 may last for a third time duration. The third detection power811 to 815 may have the same power value, or different power values asillustrated in FIG. 8.

The second detection power 801 and 802 may drive the wireless powerreceiver 450. In addition, the second detection power 801 and 802 mayhave a power amount sufficient to drive the controller and/or thecommunication unit of the wireless power receiver 450.

The wireless power transmitter 400 may apply the second detection power801 and 802 and the third detection power 811 to 815 respectively withthe second and third periods to the wireless power receiver 450. If thewireless power receiver 450 is placed on the wireless power transmitter400, an impedance viewed from a point of view of the wireless powertransmitter 400 may be changed. The wireless power transmitter 400 maydetect an impedance change during an application of the second detectionpower 801 and 802 and the third detection power 811 to 815. For example,the wireless power transmitter 400 may detect an impedance change duringapplication of the third detection power 815. Therefore, the wirelesspower transmitter 400 may detect an object in step S707 in FIG. 7. If noobject is detected in step S707, the wireless power transmitter 400 maybe kept in the power save mode in which it applies different types ofpower periodically in step S705.

If the wireless power transmitter detects an object due to an impedancechange in step S707, the wireless power transmitter 400 may enter thelow power mode in step S709. In the low power mode, the wireless powertransmitter 400 applies a driving power having a power amount sufficientto drive the controller and/or the communication unit of the wirelesspower receiver 450. For example, the wireless power transmitter 400 mayapply driving power 820 to the power transmission unit in FIG. 8. Thewireless power receiver 450 may receive the driving power 820 and drivethe controller and/or the communication unit with the driving power 820.The wireless power receiver 450 may communicate with the wireless powertransmitter with the driving power 820 in a predetermined communicationscheme. For example, the wireless power receiver 450 may transmit andreceive data required for authentication and joining a wireless powernetwork managed by the wireless power transmitter 400 based on the data.

Subsequently, the wireless power transmitter 400 may enter the powertransfer mode in which it transmits charging power in step S711 in FIG.7. For example, the wireless power transmitter may apply charging power821 and the charging power 821 may be transmitted to the wireless powerreceiver, as illustrated in FIG. 8.

In the power transfer mode, the wireless power transmitter 400 maydetermine whether an error has occurred. The error may be the presenceof a rogue object on the wireless power transmitter 400, a crossconnection, an overvoltage condition, an overcurrent condition, or anovertemperature condition. The wireless power transmitter 400 mayinclude a sensing unit for measuring an overvoltage condition, anovercurrent condition, or an overtemperature condition. For example, thewireless power transmitter 400 may measure a voltage or current at areference point and may determine that a measured voltage or currentexceeding a threshold satisfies an overvoltage or overcurrent condition.Alternatively, the wireless power transmitter 400 may include atemperature sensor and the temperature sensor may measure a temperatureat a reference point of the wireless power transmitter 400. If thetemperature at the reference point exceeds a threshold, the wirelesspower transmitter may determine that an overtemperature condition issatisfied.

If the wireless power transmitter determines an overvoltage,overcurrent, or overtemperature state according to a measured voltage,current, or temperature value, the wireless power transmitter preventsovervoltage, overcurrent, or overtemperature by decreasing wirelesscharging power by a predetermined value. If the voltage value of thedecreased wireless charging power is below a set minimum value (forexample, the minimum voltage value V_(RECT) _(—) _(MIN) _(—) _(DYN) atthe output of the rectifier of the wireless power receiver 450),wireless charging is discontinued and thus a voltage set value may bere-adjusted according to an embodiment of the present invention.

While presence of a rogue object on the wireless power transmitter isshown as an error in FIG. 8, the error is not limited to the presence ofa rogue object. Thus, it will be readily understood by those skilled inthe art that the wireless power transmitter 400 may operate in a similarmanner regarding the presence of a rogue object, a cross connection, anovervoltage condition, an overcurrent condition, and an overtemperaturecondition.

If no error occurs in step S713 in FIG. 7, the wireless powertransmitter 400 may maintain the power transfer mode in step S711. Onthe other hand, if an error occurs in step S713, the wireless powertransmitter 400 may enter the latch fault mode in step S715. Forexample, the wireless power transmitter 400 may apply first power 831 to835 as illustrated in FIG. 8. Further, the wireless power transmitter400 may output an error notification including at least one of lampillumination or a warning sound during the latch fault mode. If it isdetermined that the rogue object or the wireless power receiver has notbeen removed in step S717 in FIG. 7, the wireless power transmitter maymaintain the latch fault mode in step S715. On the contrary, if it isdetermined that the rogue object or the wireless power receiver has beenremoved in step S717, the wireless power transmitter may reenter thepower save mode in step S719. For example, the wireless powertransmitter may apply second power 851 and 852 and third power 861 to865 in FIG. 8.

An operation of a wireless power transmitter 400 upon occurrence of anerror during transmission of charging power is described above. Adescription is given below of an operation of the wireless powertransmitter 400, when a plurality of wireless power receivers 450 placedon the wireless power transmitter 400 receive charging power from thewireless power transmitter 400.

FIG. 9 is a flowchart of a method of controlling a wireless powertransmitter 400 according to an embodiment of the present invention. Thecontrol method of FIG. 9 is described below in detail with reference toFIG. 10. FIG. 10 is a graph illustrating amounts of power applied by thewireless power transmitter 450 with respect to a time axis according tothe flowchart of FIG. 9.

Referring to FIG. 9, the wireless power transmitter 400 may transmitcharging power to a first wireless power receiver 450 in step S901.Further, the wireless power transmitter 400 may additionally allow asecond wireless power receiver to join the wireless power network instep S903. The wireless power transmitter may also transmit chargingpower even to the second wireless power receiver in step S905. Inaddition, the wireless power transmitter 400 may apply the sum of thecharging power required for the first wireless power receiver and thecharging power required for the second wireless power receiver to powerreception units of the first and second wireless power receivers.

Steps S901 to S905 are illustrated in FIG. 10. For example, the wirelesspower transmitter 400 may maintain the power save mode in which thewireless power transmitter 400 applies second detection power 1001 and1002 and third detection power 1011 to 1015. Subsequently, the wirelesspower transmitter 400 may detect the first wireless power receiver andenter the low power mode in which the wireless power transmitter 400maintains detection power 1020. Then, the wireless power transmitter 400may enter the power transfer mode in which the wireless powertransmitter 400 applies first charging power 1030. The wireless powertransmitter 400 may detect the second wireless power receiver and mayallow the second wireless power receiver to join the wireless powernetwork. In addition, the wireless power transmitter 400 may applysecond charging power 1040 being the sum of the charging power requiredfor the first wireless power receiver and the charging power requiredfor the second wireless power receiver.

Referring back to FIG. 9, while transmitting charging power to both thefirst and second wireless power receivers in step S905, the wirelesspower transmitter may detect an error in step S907. As described above,the error may be the presence of a rogue object, a cross connection, anovervoltage condition, an overcurrent condition, or an overtemperaturecondition. If no error occurs in step S907-N, the wireless powertransmitter may continue to apply second charging power 1040.

On the other hand, if an error occurs in step S907, the wireless powertransmitter 400 may enter the latch fault mode in step S909. Forexample, the wireless power transmitter 400 may apply first power 1051to 1055 with a first period as illustrated in FIG. 10. The wirelesspower transmitter 400 may determine whether both the first and secondwireless power receivers have been removed in step S911 in FIG. 9. Forexample, the wireless power transmitter 400 may detect an impedancechange while applying the first power 1051 to 1055. The wireless powertransmitter 400 may determine whether both the first and second wirelesspower receivers have been removed, by checking whether the impedance hasreturned to an initial value.

If it is determined that both the first and second wireless powerreceivers have been removed in step S911, the wireless power transmitter400 may enter the power save mode in step S913. For example, thewireless power transmitter 400 may apply second detection power 1061 and1062 and third detection power 1071 to 1075 respectively with second andthird periods, as illustrated in FIG. 10.

As described above, even though the wireless power transmitter 400applies charging power to a plurality of wireless power receivers, uponoccurrence of an error, the wireless power transmitter 400 may readilydetermine whether a wireless power receiver or a rogue object has beenremoved.

FIG. 11 is a block diagram of a wireless power transmitter and awireless power receiver in an SA mode according to an embodiment of thepresent invention.

Referring to FIG. 11, a wireless power transmitter 1100 may include acommunication unit 1110, a PA 1120, and a resonator 1130. A wirelesspower receiver 1150 may include a communication unit (or a WirelessPower Transfer (WPT) Communication IC) 1151, an Application Processor(AP) 1152, a Power Management Integrated Circuit (PMIC) 1153, a WirelessPower Integrated Circuit (WPIC) 1154, a resonator 1155, an InterfacePower Management IC (IFPM) 1157, a TA 1158, and a battery 1159.

The communication unit 1110 of the wireless power transmitter 1100 maybe implemented as a WiFi/BT combination IC and may communicate with thecommunication unit 1151 of the wireless power receiver 1150 in apredetermined communication scheme, for example, in BLE. For example,the communication unit 1151 of the wireless power receiver 1150 maytransmit a PRU dynamic signal having the afore-described data structureillustrated in Table 1 above to the communication unit 1110 of thewireless power transmitter 1100. As described above, the PRU dynamicsignal may include at least one of voltage information, currentinformation, temperature information and alert information of thewireless power receiver 1150.

An output power value from the PA 1120 may be adjusted based on thereceived PRU dynamic signal. For example, if an overvoltage,overcurrent, or overtemperature condition is applied to the wirelesspower receiver 1150, a power value output from the PA 1120 may bedecreased. If the voltage or current of the wireless power receiver 1150is below a predetermined value, the power value output from the PA 1120may be increased.

Charging power from the resonator 1130 of the wireless power transmitter1100 may be transmitted wirelessly to the resonator 1155 of the wirelesspower receiver 1150.

The WPIC 1154 may rectify the charging power received from the resonator1155 and perform DC/DC conversion on the rectified charging power. TheWPIC 1154 may drive the communication unit 1151 or charge the battery1159 with the converted power.

A wired charging terminal may be inserted into the TA 1158. A wiredcharging terminal such as a 30-pin connector or a Universal Serial Bus(USB) connector may be inserted into the TA 1158. The TA 1158 mayreceive power from an external power source and charge the battery 1159with the received power.

The IFPM 1157 may process the power received from the wired chargingterminal and output the processed power to the battery 1159 and the PMIC1153.

The PMIC 1153 may manage power received wirelessly or wiredly and powerapplied to each component of the wireless power receiver 1150. The AP1152 may receive power information from the PMIC 1153 and control thecommunication unit 1151 to transmit a PRU dynamic signal for reportingthe power information.

A node 1156 connected to the WPIC 1154 may also be connected to the TA1158. If a wired charging connector is inserted into the TA 1158, apredetermined voltage, for example, 5V may be applied to the node 1156.The WPIC 1154 may determine whether the wired charging adaptor has beeninserted by monitoring a voltage applied to the node 1156.

The AP 1152 has a stack of a predetermined communication scheme, forexample, a WiFi/BT/BLE stack. Accordingly, the communication unit 1151for communication for wireless charging may load the stack from the AP1152 and then communicate with the communication unit 1110 of thewireless power transmitter 1100 based on the stack by WiFi/BT/BLE.

However, it may occur that data for wireless power transmission cannotbe retrieved from the AP 1152 due to a OFF state of the AP 1152 or poweris insufficient to maintain an ON state of the AP 1152 during retrievingthe data from a memory of the AP 1152 and using the retrieved data.

If the residual power amount of the battery 1159 is below a minimumpower limit as described above, the AP 1152 may be turned off and thebattery 1159 may be wirelessly charged using some components forwireless charging in the wireless power receiver 1150, for example, thecommunication unit 1151, the WPIC 1154, and the resonator 1155. A statein which power sufficient to turn on the AP 1152 cannot be supplied maybe referred to as a dead battery state.

Because the AP 1152 is not operated in the dead battery state, thecommunication unit 1151 may not receive the stack of the predeterminedcommunication scheme, for example, the WiFi/BT/BLE stack from the AP1152. In anticipation of this case, a part of the stack of thepredetermined communication scheme, for example a BLE stack, may befetched from the AP 1152 and stored in a memory 1162 of thecommunication unit 1151. Accordingly, the communication unit 1151 maycommunicate with the wireless power transmitter 1100 using the stack ofthe communication scheme stored in the memory 1162, that is, a wirelesscharging protocol, for wireless charging. The communication unit 1151may have an internal memory. The BLE stack may be stored in a Read OnlyMemory (ROM) in the SA mode.

As described above, a mode in which the communication unit 1151communicates using the stack of the communication scheme stored in thememory 1162 may be referred to as the SA mode. Accordingly, thecommunication unit 1151 may manage the charging procedure based on theBLE stack.

According to an embodiment of the present invention, if the battery 1159of the wireless power receiver 1150 is in the dead battery state, or ifthe AP 1152 cannot receive the BLE stack from the communication unit1151 as the AP is not operated in the state where the wireless powerreceiver 1150 is powered off, the wireless power receiver 1150 may nottransmit an advertisement signal through the communication unit 1151within a predetermined time, after receiving a beacon signal from thewireless power transmitter 1100.

For example, according to the A4WP standard, the wireless powertransmitter 1100 may transmit a long-beacon signal, and upon receivingthe long-beacon signal, the wireless power receiver 1150 may transmit anadvertisement signal to the wireless power transmitter 1100 within apredetermined time, thereby proceeding with a registration procedure forwireless charging.

However, as described above, if a boot procedure for operating the AP1152 is required while the battery power of the wireless power receiver1150 is low or depleted, or the wireless power receiver 1150 is poweredoff, the wireless power receiver 1150 may not transmit an advertisementsignal to the wireless power transmitter 1100 through the communicationunit 1151 within a predetermined time. If the wireless power receiver1150 cannot transmit an advertisement signal within a predetermined timein this way, the normal registration procedure may not be performed,making it impossible to wirelessly charge the wireless power receiver1150.

Reference will now be made to FIGS. 12 to 17 for a description ofvarious embodiments of extending a transmission period of a beaconsignal to make it possible to receive an advertisement signal within apredetermined time despite the delay in the time that is required untilthe advertisement signal is transmitted through the communication unit1150 after the AP 1152 of the wireless power receiver 1150 is executed.

With reference to FIGS. 1 to 11, a wireless charging system according tothe present invention is described above. A method of transmitting asignal by a wireless power transmitter in a wireless charging system,and a wireless power transmitter and a wireless power receiver accordingto an embodiment of the present invention, is described below in detailwith reference to FIGS. 12 to 17.

FIG. 12 is a graph illustrating transmission of a beacon signalaccording to an embodiment of the present invention.

Referring to FIG. 12, a wireless power transmitter (PTU) mayperiodically apply a current I_(TX) _(—) _(LONG) _(—) _(BEACON) fortransmission of a long-beacon signal to its PTU resonator in the powersave mode or the power save state. The wireless power transmitter mayapply the current I_(TX) _(—) _(LONG) _(—) _(BEACON) for transmission ofa long-beacon signal within 10 ms in which a short-beacon signal isterminated.

For example, according to a standard document, a period t_(LONG) _(—)_(BEACON) in which the long-beacon signal is transmitted may be 105 ms±5ms, if the wireless power transmitter does not leave the power savemode. The period t_(LONG) _(—) _(BEACON) may be shorter. For example, aperiod t_(LONG) _(—) _(BEACON) _(—) _(PERIOD) in which the long-beaconsignal is transmitted may be 850 ms or more, but does not exceed 3seconds.

Upon receiving an advertisement signal related to a wireless powertransmission service while the long-beacon signal is transmitted, thewireless power transmitter may be switched to the low power mode or thelow power state and transmit a connection request within 0 to 50 ms. Theadvertisement signal should meet the following conditions:

the Received Signal Strength Indicator (RSSI) of an advertisement signalis greater than ADV_PWR_MIN that is measured at a receiving antenna; and

the wireless power transmitter monitors a change in impedance at aroundthe time of the advertisement time.

If all of these conditions are not satisfied, the wireless powertransmitter may ignore the advertisement signals from the wireless powerreceiver. If one of the conditions is satisfied and if, for example, aneleventh advertisement signal is received, or more than 1700 ms haselapsed, the wireless power transmitter may transmit a connectionrequest.

After the connection request, the wireless power transmitter maymaintain the power level for 500 ms, for registration of the wirelesspower receiver.

If the battery power of the wireless power receiver is depleted or thewireless power receiver is in the dead battery state, the wireless powerreceiver may not transmit an advertisement signal within 110 ms. If thewireless power supplied by the wireless power transmitter cannot wakethe communication unit (e.g., a BLE chip of the communication unit)within 110 ms, it may be impossible to wirelessly charge the wirelesspower receiver.

FIG. 13 is a graph illustrating transmission of a beacon signalaccording to an embodiment of the present invention.

Referring to FIG. 13, if the wireless power receiver is not awakened bythe wireless power (e.g., a short-beacon signal or a long-beacon signal)transmitted from the wireless power transmitter, the wireless powerreceiver must receive the power supplied from its own battery.

In a case where the battery of the wireless power receiver is depletedor the wireless power receiver is in the dead battery state, if theperiod in which the wireless power is supplied from the wireless powertransmitter is not long enough to charge the battery and wake up thecontroller (e.g., an MCU chip), the wireless power receiver may nottransmit the advertisement signal for entering the low power mode.

For example, according to a wireless charging standard document, atransmission period of a long-beacon signal is only 105 ms±5 ms, whichmay be too short to wake up the controller (e.g., the AP 1152 in FIG.11) of the wireless power receiver and send an advertisement signal tothe wireless power transmitter.

For this reason, the wireless power receiver must extend the long-beacontransmission period to a sufficient period to charge the battery andwake up the controller.

Therefore, according to an embodiment of the present invention, thewireless power transmitter may check a load change more than once beforethe long-beacon transmission period (e.g., about 100 ms) is terminated.In addition, according to an embodiment of the present invention, thewireless power receiver may generate a load change that can be detectedby the wireless power transmitter before the long-beacon transmissionperiod is terminated.

In other words, before the long-beacon transmission period isterminated, the wireless power receiver may generate a load change andthe wireless power transmitter may detect the load change and extend thelong-beacon transmission period by an additional long-beacontransmission period. According to an embodiment of the presentinvention, as the wireless power receiver generates a load change withinthe long-beacon transmission period, the wireless power transmitter maycontinue to extend the long-beacon transmission period.

Since the wireless power transmitter can detect a load change beforetermination of the long-beacon transmission period and extend thelong-beacon transmission period by another long-beacon signaltransmission period, the wireless power receiver may maintain thelong-beacon signal transmission period by periodically generating a loadchange. The periodic load change may be generated by a dummy load or anequivalent circuit.

Accordingly, the wireless power receiver may extend the transmissionperiod of the long-beacon signal until the battery of the wireless powerreceiver is charged or the wireless power receiver supplies sufficientpower to wake up the controller.

In addition, according to an embodiment of the present invention, sincethe wireless power transmitter must save power, the wireless powertransmitter may limit the number of extensions for the long-beaconsignal of the wireless power receiver, or the wireless power transmittermay extend the transmission time of the long-beacon signal only up to apredetermined time (e.g., 7 seconds). The predetermined time may be setto a time that is sufficient to wake up the controller of the wirelesspower receiver and receive an advertisement signal from the wirelesspower receiver.

FIG. 14 is a flowchart illustrating a beacon signal transmissionprocedure according to an embodiment of the present invention.

Referring to FIG. 14, in the power save mode in step S1402, the wirelesspower transmitter may transmit a short-beacon signal or a long-beaconsignal in every predetermined period during a predetermined period oftime in step S1404. If the predetermined long-beacon transmission periodis terminated in step S1406, the transmission of the long-beacon signalmay be terminated in step S1408 and the long-beacon signal may betransmitted again upon arrival of the next transmission period.

According to an embodiment of the present invention, if a load change ofthe wireless power receiver is detected in step S1410 before thetransmission of the long-beacon signal is terminated in step S1406 (orduring the transmission of the long-beacon signal), the predeterminedtransmission period of the long-beacon signal may be extended in stepS1412.

FIG. 15 is a graph illustrating transmission of a beacon signalaccording to an embodiment of the present invention.

Referring to FIG. 15, in an embodiment of the present invention, awireless power receiver may make a request to extend a long-beaconsignal transmission period using an in-band signal.

For example, as illustrated in FIG. 15, before the long-beacontransmission period is terminated, if the wireless power transmitterdemodulates an in-band signal and detects a predetermined code or signalas a result of the demodulation, the wireless power transmitter mayextend the transmission period of the long-beacon signal by apredetermined period.

The transmission period of the long-beacon signal may be extended bytaking into account the time that is sufficient to supply power to acontroller of a wireless power receiver and transmit an advertisementsignal to the wireless power transmitter.

According to an embodiment of the present invention, a long-beaconextension request signal that is transmitted in the in-band signal maybe configured as a predetermined code or pulse signal. Accordingly, thewireless power transmitter may check the predetermined code or pulse byanalyzing or demodulating the in-band signal, to thereby extend thelong-beacon signal transmission period by a predetermined period.

According to an embodiment of the present invention, if the wirelesspower transmitter desires to transmit the long-beacon extension requestsignal using an in-band signal, the wireless power receiver may includea dummy load or a load modulation circuit. Upon receiving a short-beaconsignal or a long-beacon signal from the wireless power transmitter, thewireless power receiver may transmit information using an in-band signalby switching a circuit connected to the dummy load or changing a loadthrough the load modulation circuit.

The wireless power transmitter may further include a circuit capable ofdemodulating the load change from the in-band signal, and may detect along-beacon extension request signal included in the in-band signal bydemodulating and/or decoding the in-band signal.

FIG. 16 is a flowchart of a beacon signal transmission procedureaccording to an embodiment of the present invention. Referring to FIG.16, in the power save mode in step S1602, the wireless power transmittermay transmit a short-beacon signal or a long-beacon signal in everypredetermined period during a predetermined period of time in stepS1604. If the predetermined long-beacon transmission period isterminated, the transmission of the long-beacon signal may beterminated, and the long-beacon signal may be transmitted again uponarrival of the next transmission period.

According to various embodiments of the present invention, the wirelesspower transmitter may demodulate an in-band signal in step S1606, beforethe transmission of the long-beacon signal is terminated (or during thetransmission of the long-beacon signal). If a code or signalcorresponding to a predetermined long-beacon extension request signal isincluded in the in-band signal as a result of the demodulation in stepS1608, the wireless power transmitter may extend the predeterminedtransmission period of the long-beacon signal by a predetermined periodin step S1610.

FIG. 17 is a block diagram of a wireless power receiver according to anembodiment of the present invention.

Referring to FIG. 17, the wireless power receiver may include a powerreception unit 1701, a rectifier 1702, a DC/DC converter 1703, a controlcircuit 1704, a load switch 1707, and a load 1708.

An AC current received at the power reception unit 1701 may be convertedinto a DC current in the rectifier 1702. According to an embodiment ofthe present invention, the control circuit 1704 may be driven by theconverted DC current, and may generate a control signal capable ofcontrolling the load switch 1707 by a predetermined circuit.

For example, if the wireless power transmitter transmits a short-beaconsignal or a long-beacon signal as described above, the control circuit1704 may be driven by a signal that is received through the powerreception unit 1701. Therefore, for example, the control circuit 1704may be driven by the received short-beacon signal or long-beacon signal,and may control the load switch 1707 before the transmission of thelong-beacon signal is terminated, to thereby generate a load change. Thecontrol circuit 1704 may be configured as a separate circuit independentof the controller of the wireless power receiver, and may be driven bythe received current even before the controller (e.g., the AP) of thewireless power receiver is driven.

If the wireless power receiver generates a load change before thetermination of the transmission of the long-beacon signal in this way,the wireless power transmitter may detect the load change and extend thetransmission period of the long-beacon signal according to an embodimentof the present invention.

According to an embodiment of the present invention, the control circuit1704 may be connected between the power reception unit 1701 and therectifier 1702, and receive an AC current. Although the control circuit1704 is illustrated to control ON/OFF of the load switch 1707 in FIG.17, the control circuit 1704 may be configured to switch a connection ofa dummy load provided in addition to the load 1708.

The above-described load change generation method and circuitillustrated in FIG. 17 may be utilized in various ways for devicedetection, long-beacon extension, cross connection prevention anddetection, rogue device detection, in-band signaling and the like.

As is apparent from the foregoing description, according to anembodiment of the present invention, even in the case where the batterypower of the wireless power receiver is low or depleted or where theboot procedure is required to operate the processor of the wirelesspower receiver, the wireless power transmitter may receive anadvertisement signal within a predetermined time by detecting a loadchange.

In addition, according to an embodiment of the present invention, evenin the case where the battery power of the wireless power receiver islow or depleted or where the boot procedure is required to operate theprocessor of the wireless power receiver, the wireless power transmittermay receive an advertisement signal within a predetermined time byreceiving a predetermined signal from the wireless power receiver.

While the present invention has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the scope and spirit of the present invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method of transmitting a signal by a wirelesspower transmitter in a wireless charging system, the method comprising:transmitting a first signal; transmitting a second signal; detecting aload change during a period in which the second signal is transmitted;and extending a transmission period of the second signal based on thedetected load change.
 2. The method of claim 1, wherein the first signalis a short-beacon signal and the second signal is a long-beacon signal.3. The method of claim 1, wherein the first signal is transmitted inevery first period, and the second signal is transmitted in every secondperiod.
 4. The method of claim 1, further comprising receiving anadvertisement signal from a wireless power receiver.
 5. The method ofclaim 1, wherein extending the transmission period of the second signalcomprises extending the transmission period of the second signal, if aload change is detected a predetermined number of times or more duringthe period in which the second signal is transmitted.
 6. The method ofclaim 1, wherein extending the transmission period of the second signalfurther comprises extending the transmission period of the second signalby the transmission period of the second signal.
 7. The method of claim1, further comprising: decoding an in-band signal from a wireless powerreceiver during the period in which the second signal is transmitted;and if the decoded signal corresponds to a predetermined value,determining the decoded signal as an extension request signal fortransmission of the second signal.
 8. A wireless power transmitter,comprising: a power transmission unit configured to transmit a firstsignal and a second signal; a sensing unit configured to detect a loadchange during a period in which the second signal is transmitted; and acontroller configured to extend a transmission period of the secondsignal based on the detected load change.
 9. The wireless powertransmitter of claim 8, wherein the first signal is a short-beaconsignal and the second signal is a long-beacon signal.
 10. The wirelesspower transmitter of claim 8, wherein the first signal is transmitted inevery first period, and the second signal is transmitted in every secondperiod.
 11. The wireless power transmitter of claim 8, wherein thecontroller is configured to receive an advertisement signal from awireless power receiver, and to handle registration of the wirelesspower receiver.
 12. The wireless power transmitter of claim 8, whereinthe controller is configured to extend the transmission period of thesecond signal, if a load change is detected a predetermined number oftimes or more during the period in which the second signal istransmitted.
 13. The wireless power transmitter of claim 8, wherein thecontroller is configured to further extend the transmission period ofthe second signal by the transmission period of the second signal. 14.The wireless power transmitter of claim 8, further comprising: adecoding unit configured to decode an in-band signal from a wirelesspower receiver during the period in which the second signal istransmitted; and wherein if the decoded signal corresponds to apredetermined value, the controller is further configured to determinethe decoded signal as an extension request signal for transmission ofthe second signal.
 15. A wireless power receiver, comprising: a powerreception unit configured to receive a first signal and a second signal;a control circuit that is electrically connected to the power receptionunit, and configured to generate a control signal for a load changebased on the first signal or the second signal received from the powerreception unit; and a switching unit that is provided between the powerreception unit and a load, and configured to switch a connection betweenthe power reception unit and the load based on the control signal fromthe control circuit.
 16. The wireless power receiver of claim 15,wherein the first signal is a short-beacon signal and the second signalis a long-beacon signal.
 17. The wireless power receiver of claim 15,wherein the first signal is transmitted in every first period, and thesecond signal is transmitted in every second period.
 18. The wirelesspower receiver of claim 15, further comprising a communication unitconfigured to transmit an advertisement signal in response to receptionof the second signal.
 19. The wireless power receiver of claim 15,wherein the control circuit is configured to generate a control signalfor a load change, a number of which is greater than or equal to apredetermined number of times, in response to the received first signalor second signal.
 20. The wireless power receiver of claim 15, whereinthe control circuit is configured to generate a predetermined code orsignal for requesting extension of transmission of the second signal, inresponse to the received first signal or second signal.